The present invention is related to an improved method for making aliphatic diperoxyacids having from about 8 to about 16 carbon atoms, preferably from 11 to about 16 carbon atoms, and most preferably 12 carbon atoms.
Peroxygen bleaching agents in general and peroxyacid compounds in particular have long been recognized as effective bleaching agents for use when the adverse color and fabric damage effects of harsh halogen active bleaching agents cannot be tolerated. See, for example, Canadian Pat. No. 632,620, Jan. 30, 1962, to McCune. This attractive nature of peroxyacid compounds (particularly diperoxydodecanedioic acid) makes it desirable to be able to make them in the most economical manner.
The prior art teaches the making of peroxyacid compounds in several ways. Parker et al. in Journal American Chemical Society, 79, 1929 (1957), disclose making diperoxyacids by dissolving a dibasic acid in sulfuric acid and adding hydrogen peroxide dropwise. U.S. Pat. No. 3,079,411, Feb. 26, 1963, to Silbert et al., discloses forming long chain aliphatic peroxyacids by combining an aliphatic acid with an alkanesulfonic acid and then treating the combination with an excess of hyrogen peroxide. U.S. Pat. No. 2,813,896, Nov. 19, 1957, to Krimm, discloses forming peroxyacids by combining sulfuric acid and hydrogen peroxide and subsequently treating the combination with a carboxylic acid. The reaction is conducted so that there is at least one mole of sulfuric acid present at the end of the reaction for every six moles of water. All of the above disclosed methods utilize the batch manufacturing approach.
The use of continuous processes for making diperoxyacids has also been disclosed. See, for example, U.S. Pat. No. 3,235,584, Feb. 15, 1966, to Blumbergs wherein it is disclosed to react an organic acid halide with an alkali metal or alkaline earth metal peroxide to form a salt of a peroxycarboxylic acid. Also U.S. Pat. No. 3,284,491, Nov. 8, 1966, to Korach et al. wherein a peroxyacid is formed in a single liquid phase.
While the prior art teaches several methods for making peroxyacids, it does not suggest the advantages for using a continuous stirred reactor for making peroxyacids of the type disclosed herein utilizing the sulfuric acid, water, hydrogen peroxide reaction medium. The present inventors have discovered that a continuous reactor can produce aliphatic diperoxyacids having significantly larger crystals than those formed from a batch process. This allows for the crystals to be collected more easily and economically due to increased filtration rates.
It is therefore an object of the present invention to provide a method for making diperoxyacids which have increased crystal size.
This and other objects of the present invention will become apparent from the following description.
All percentages and ratios used herein are by weight unless otherwise specified.